1. Field of the Invention
The present invention relates to an image sensor unit as well as a paper sheet distinguishing apparatus, an image reading apparatus and an image forming apparatus to which the image sensor unit is applied.
2. Description of the Related Art
An image sensor unit that reads a bill or an original as an object of illumination is used in a paper sheet distinguishing apparatus, an image reading apparatus and an image forming apparatus. Conventionally, such kind of image sensor unit includes a light source, a light guide that shapes light emitted from the light source into a line, a light condenser that condenses light from an object of illumination that is a reading target, and an image sensor that detects light from the object of illumination. These optical members and elements and the like are housed in a frame of the image sensor unit and are covered by a cover member attached to the frame. In some cases, a double-sided tape is used to bond the frame and the cover member.
According to this configuration, since a force in a shearing direction is applied to the double-sided tape when the frame and cover member expand due to heat generated by the light source or the like, there is a risk that the double-sided tape will peel off from the frame or the cover member. Further, even in a case where the double-sided tape does not peel off, there is a risk that the image sensor unit will curve due to a difference between thermal deformation amounts of the frame and the cover member.
In Japanese Laid-open Patent Publication No. 2010-283436, as a configuration that suppresses the influence of temperature variations in a reading apparatus, a configuration is disclosed that prevents positional displacement between a light source and a light guide that is caused by a difference between thermal deformation amounts of a frame and the light guide. However, a configuration that prevents or suppresses peeling off of a double-sided tape or deformation of an image sensor unit that is caused by a difference between thermal deformation amounts of a frame and a cover member is not disclosed.